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The AFC module allows read out of the total flow supplied to system - this is ideal for setting split and
trap / desorb flows and for troubleshooting leaks.
d.
To view the total flow supplied press the “FLOW” key on the GC keypad as above.
e.
The Total Flow in ml/min is always displayed (above the Split Mode) as shown above.
The septum purge flow should be set to a flow rate of around 5 ml/min
f.
To set the septum purge flow display the “FLOW” screen as described above.
g.
Press the button to the right of the “PF3” key (below the screen) as shown below. This displays a
second set of commands for the PF keys.
Extending the PF commands
h.
Select the purge command on “PF3” and enter the desired value. A flow rate of 2-5 ml/min is
recommended.
Setting the septum purge flow value
6.3.3
Flow stability
AFC works with both impeded (traps containing porous polymer e.g. Tenax) and un-impeded (traps only
containing carbon sorbents) traps, with no carrier gas instability generally noted (even with 90-100 psi
supplied to the inlet of the AFC system). However should any instability in the carrier gas occur it may be
necessary to dampen the reaction of the AFC controller.
Press the “FUNC” key on the GC keypad.
Enter “7”, enter “5”, enter “1201”, enter “1”. This will display the “Flow Adjust” page.
For instruments with two or more AFC units, press the “PF2” button to select the correct flow unit.
Move the cursor to the “I Time” entry in the “Flow” column.
Change the value from “1” to “4” then press the “Enter” key.